A common reason for the Index Status count to go down at the "update" is that an alternate version of the website is verified in Webmaster Tools. A simple way to double-check that is to do a site:-query for just your domain name (eg https://www.google.com/#q=site:fish.com ), and to see which version is shown. If the www-version is shown, then that's the version where most of your data will be. If you want to be on the safe side, just verify both of them.
OK. Here are the screenshots for my GWT Index question. +David Quaid +David Harry 
2 Photos - View album
Shared publiclyView activity